The present invention relates generally to ferrite suppressors for suppressing high frequency noise in electrical cables, and more particularly to holders for such ferrite suppressors as are designed to encompass the electrical cable and be locked in position about the cable by way of integrally molded tabs included in the holders.
Typical ferrite suppressors are manufactured of ferrous oxide material that is formed into the shape of a cylinder having a hole aligned with the major axis of revolution of the cylinder for receiving an electrical cable. Electrical cables, whether intended to carry power or for communication, can act as antennas that pick up spurious noise signals from various sources. The ferrite suppressors are employed in close proximity to electrical equipment to which the electrical cables are attached to screen the electrical equipment from the spurious signals while allowing desirable signals to pass through.
The ferrite suppressors are typically split or bifurcated along the major axis of revolution so that the suppressors can be joined over the desired location on the electrical cable rather than requiring that the cable be threaded through to the desired position. The bifurcated halves of the ferrite suppressors can be secured in position using any number of techniques. Increasingly, the bifurcated halves are secured in position through the use of special holders that are designed to receive the two halves and snap together around the electrical cable. Examples of prior art holders are to be found in U.S. Pat. Nos. 5,355,109; 5,162,772; 5,003,278; 4,882,561; and 4,825,185.
The prior art holders generally have two halves, with each half of the holder intended to receive one half of the ferrite suppressor. Each half includes two ends, each end containing a generally semicircular notch adapted to receive a cable to which the suppressor is to be applied. In many of the prior art holders, the two halves of the holder are typically molded as a single unit and include a molded living hinge along a first side parallel to the major axis of revolution of the suppressor. The first sides of the two halves are maintained in close proximity to each other by the living hinge while the second sides of the two halves, which are farthest from the living hinge, can swing toward and away from each other. In a typical holder of the prior art, the second sides include interlocking tabs or other complementary structures that secure the two halves of the holder together around the electrical cable.
The proper dimensioning of the hinge portion joining the first sides of the two halves together often presents an appreciable problem that must take into account both the geometry of the situation and the stiffness or flexibility of the resin employed to form the holder. If the hinge is too short, the hinge may not provide sufficient flexibility to permit the holder to close around the electrical cable. If the hinge is too long, the holder and ferrite suppressor may be inadequately secured to the electrical cable. To address this problem prior art holders have included a plurality of fingers or pinching members in the immediate vicinity of the semicircular notches in the ends of the holder to ensure fixed engagement with the electrical cable over some modest range of dimensions. While such structures are generally satisfactory to achieve retention of the ferrite suppressor at a fixed location on an electrical cable, the pressures exerted on the cable can still be unbalanced if the dimension of the hinge is not carefully selected.
It is therefore an object of the present invention to reduce the criticality of the hinge dimension. It is a further object to provide a balanced force on both sides of the electrical cable to which the ferrite suppressor holder is secured.
A holder of the present invention for containing a split ferrite suppressor includes two halves hinged to each other along one side. Each half includes a recess adapted to hold one portion of the split ferrite suppressor. Each half also includes two ends, each end containing a generally semicircular notch adapted to receive a cable to which the suppressor is to be applied. The ends also have locking tabs disposed on both side of the semicircular notch for locking the two halves of the holder together.
The locking tabs are preferably arranged as confronting mating pairs of male and female elements, each element having a head portion and a neck portion smaller than the head portion. The interlocking tabs preferably include tapering surfaces connecting the head and neck portions, the tapering surfaces applying a biasing force tending to hold the two halves of the holder together. The tapering surfaces are preferably substantially planar surfaces inclined at about 10xc2x0 with respect to a line bifurcating said head and neck portions.
In one embodiment of the holder of the present invention, the male elements are all located on one half and the female elements are all located on the other half. In the preferred embodiment of the present invention, the head portion of each of the male and female elements is about 20% larger than the neck portion.
The holder of the present invention preferably includes a plurality of resilient fingers inclined outwardly from each semicircular notch, each resilient finger having a rounded end for engaging a cable to which the suppressor is applied to resist longitudinal movement of the suppressor with respect to the cable.
An important feature of the present invention is the presence of locking tabs disposed on both side of the semicircular notch in both ends of the holder for locking the two halves of the holder together. This disposition of locking tabs has the advantage of balancing the force applied to the electrical cable to which the ferrite suppressor holder is secured. This feature is enhanced by the incorporation of the plurality of resilient fingers inclined outwardly from each semicircular notch for engaging the electrical cable to which the suppressor is applied. Other features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiment of the invention shown in the accompanying drawings.